The format converter of the Main Profile of the MPEG-H 3D Audio standard is a downmixer that converts multichannel audio signals from transmitted channel configurations with Nin channels to desired reproduction formats with Nout≤Nin channels. This downmixer features a phase-alignment active downmix algorithm that ensures energy preservation and moreover serves to prevent or reduce uncontrolled signal cancellations or signal amplifications that would otherwise result in unwanted signal coloration and artefacts. On the downside, the downmix algorithm has high computational complexity and imparts high computational load on the decoder. For example, for a downmix from 22.2 channels to stereo, about 50 percent of the full decoder complexity in the Main Profile are allotted to the downmix algorithm.
High computational complexity foremost arises for a large number Nin of input channels. Computational load is especially critical for devices that typically have comparably small computation power, but render high-quality broadcasting content characterized by a large number of channels.
Thus, there is a need for a simple and efficient format converter that still maintains the advantageous properties with regard to audio signal quality and energy preservation.